Reading device and image forming device

Abstract

To prevent an unnecessary reduction in productivity and loss of a recording medium.SOLUTION: A reading device comprises: an image reading unit that reads an image on a recording medium to be conveyed; a background unit that is the background of image reading performed by the image reading unit; and a foreign substance detection unit that compares a first read image obtained by reading the background unit with the image reading unit and a second read image obtained by reading the background unit and the recording medium with the image reading unit with each other and detects attachment of a foreign substance.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a reading device and an image forming device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in an image forming apparatus, a technique is known in which an image formed on a sheet is read and the image formed on the sheet is inspected to see if it is normal.

[0003] Patent Document 1 also discloses a technique for acquiring data of a reference white board in a print image reading area in advance when there is no print image, and correcting shading data according to changes in the level of the read data of the reference white board at both ends of the main scanning direction outside the print image reading area.In addition, Patent Document 1 discloses a technique for changing the data acquisition position using a rotation mechanism when dirt is found on the reference white board outside the print image reading area at both ends of the main scanning direction. Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the conventional technology, image inspection was stopped even when foreign matter such as dirt was found in a position that did not affect the image inspection, which resulted in unnecessary reduction in productivity and loss of recording media.

[0005] The present invention has been made in view of the above, and has as its object to prevent unnecessary decline in productivity and loss of recording media. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a reading device of the present invention includes an image reading unit that reads an image on a recording medium being conveyed, a background portion that serves as a background for image reading by the image reading unit, and a foreign matter detection unit that detects adhesion of a foreign matter to a part of a reading path of the image reading unit and a location of the foreign matter by comparing a first read image of the background portion read by the image reading unit with a second read image of the background portion and the recording medium read by the image reading unit, and the foreign matter detection unit but , the location where the foreign matter is attached is When the image reading unit reads the recording medium, If it is determined that the foreign matter is in a position that is hidden by the recording medium, it is not necessary to remove the foreign matter. [Effects of the Invention]

[0007] The present invention has the effect of preventing unnecessary decline in productivity and loss of recording media. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of the second reading unit of the image reading unit. [Figure 3] FIG. 3 is a block diagram showing the hardware configuration of the image reading unit. [Figure 4-1] FIG. 4A is a diagram illustrating an example of read data relating to the presence or absence of foreign matter on a background rotating body. [Figure 4-2] FIG. 4B is a diagram illustrating an example of read data relating to the presence or absence of foreign matter on the background rotating body. [Figure 5] FIG. 5 is a diagram illustrating an example of read data relating to the presence or absence of a foreign substance in an illumination device. [Figure 6] FIG. 6 is a diagram illustrating an example of how a foreign substance appears in a scanned image. [Figure 7] FIG. 7 is a flowchart showing the flow of the process for detecting the location of adhesion of a foreign substance. [Figure 8]FIG. 8 is a diagram showing a modified example of the configuration of the second reading unit. [Figure 9] FIG. 9 is a diagram illustrating an example of foreign substance inspection during shading according to the second embodiment. [Figure 10] FIG. 10 is a diagram showing an example of the image reading result when a foreign substance is present. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a reading device and an image forming device will be described in detail with reference to the accompanying drawings.

[0010] (First embodiment) 1 is a diagram showing an example of the configuration of an image forming apparatus 100 according to a first embodiment. As shown in FIG. 1, image forming apparatus 100, which is a reading device and an image forming apparatus, will be described as an example applied to a multifunction peripheral having at least two of a copy function, a printer function, a scanner function, and a facsimile function. Image forming apparatus 100 includes an image forming unit 110, a medium conveying unit 120, an image reading unit 130, and a control unit 150.

[0011] The control unit 150 controls the overall operation of the image forming apparatus 100, and controls a series of processes for forming an image on a sheet S, which is a sheet-like recording medium.

[0012] The image forming unit 110 includes photosensitive drums 112 (112Y, 112M, 112C, 112K) for forming latent images corresponding to images of each color. The photosensitive drums 112 (112Y, 112M, 112C, 112K) are arranged to correspond to the image forming process using image forming materials (for example, toners) of each color: yellow (Y), magenta (M), cyan (C), and black (K).

[0013] The photosensitive drums 112 (112Y, 112M, 112C, 112K) are arranged along an intermediate transfer belt 111, which is an endless moving means. The intermediate transfer belt 111 is looped around at least one drive roller and multiple driven rollers, and moves between a primary transfer position where an image (toner image) developed on the photosensitive drums 112 (112Y, 112M, 112C, 112K) is transferred, and a secondary transfer position where the image (toner image) is transferred to a sheet S.

[0014] A transfer unit 113 is disposed at the secondary transfer position. The transfer unit 113 includes a transfer roller 113a and an opposing roller 113b disposed opposite the transfer roller 113a. In the transfer unit 113, a toner image is transferred from the intermediate transfer belt 111 to the sheet S, thereby forming an image at a predetermined position on the sheet S. A gap is formed between the transfer roller 113a and the opposing roller 113b, large enough to allow the intermediate transfer belt 111 and the sheet S to pass through while being sandwiched between them. An image is transferred onto the sheet S while being sandwiched in this gap and being transported in the transport direction (sub-scanning direction).

[0015] The media conveying section 120 includes a supply tray 121 that stores the sheet S, a conveying path 122 along which the sheet S is conveyed and which is configured by an arrangement of multiple pairs of rollers, a fixing roller 123 that is arranged downstream in the conveying direction from the transfer section 113, a conveying path switching section 124, and a reversing path 125.

[0016] During the execution of the image forming process, under the control of a predetermined control process by the control unit 150, the sheet S stored in the supply tray 121 is separated by a pickup roller or the like and transported along the transport path 122 to the transfer unit 113.

[0017] When the sheet S reaches the transfer unit 113, a transfer process is carried out. That is, the sheet S is conveyed in a predetermined conveying direction while being sandwiched between the surface of the intermediate transfer belt 111, which is urged toward the counter roller 113b by the transfer roller 113a, and the counter roller 113b. When the sheet S passes between the intermediate transfer belt 111 and the counter roller 113b, the image forming material on the surface of the intermediate transfer belt 111 is transferred to the sheet S. By this transfer process, an image is formed on one side (first side) of the sheet S.

[0018] The sheet S with the image formed on its first surface is further conveyed, and after the image is fixed by fixing rollers 123, it is conveyed to a conveying path switching unit 124. Thereafter, the sheet S reverses its traveling direction and is conveyed to a reversing path 125. Then, the sheet S is conveyed again to the transfer position of transfer rollers 113a in a state in which the image formed on the intermediate transfer belt 111 is transferred to the second surface of the sheet S.

[0019] The sheet S with the image formed on the second side is further conveyed, and after the image on the second side is fixed by the fixing roller 123, the sheet S is conveyed to the image reading unit .

[0020] The image reading unit 130 has a first reading unit 130a that reads the first side of the sheet S and a second reading unit 130b that reads the second side of the sheet S. The sheet S that has passed through the image reading unit 130 is selectively discharged to tray 126A or tray 126B of the discharge tray 126.

[0021] The image reading unit 130 functions as an image inspection device. The image reading unit 130 detects abnormalities (streaks, omissions, stains), color changes, print position on the sheet S, etc. in the printed image formed on the sheet S, and detects that an abnormal image has been printed by detecting a difference exceeding a specified value by comparing the data with the original data.

[0022] Next, a detailed description will be given of the second reading section 130b of the image reading section 130. Here, Fig. 2 is a diagram showing the configuration of the second reading section 130b of the image reading section 130.

[0023] As shown in FIG. 2, the second reading unit 130b includes an irradiation unit 131 that irradiates the second surface of the sheet S passing through the reading position with light, a reading unit 132, and a background switching revolver 140.

[0024] The irradiation unit 131 includes a plurality of lighting devices 131a (lighting 1) and 131b (lighting 2). The first lighting device 131a and the second lighting device 131b are configured with LED (Light Emitting Diode) arrays. The irradiation unit 131 includes a glass 131c at a position facing the background switching revolver 140. The glass 131c transmits light emitted from the irradiation unit 131 and reflected light that is the irradiated light reflected by the background switching revolver 140 or the sheet S and returns.

[0025] The reading unit 132 is a reduction optical system made up of an image sensor 132a, a lens 132b, and multiple mirrors 132c. The reading unit 132 reflects light reflected by the second surface of the sheet S with the multiple mirrors 132c, collects the light with the lens 132b, and forms an image on the narrow image sensor 132a.

[0026] The second reading unit 130b reads the image printed on the second side of the sheet S as a two-dimensional image by repeatedly reading one line of an image extending in the sheet width direction in accordance with the paper passing movement of the sheet S passing through the reading position.

[0027] The background switching revolver 140 is positioned opposite the second reading unit 130b across the conveying path 122, and reflects the light irradiated onto the second surface of the sheet S when reading the image printed on the second surface of the sheet S.

[0028] As shown in FIG. 2, the background switching revolver 140 includes background rotators 140a and 140b, which are background units having a rotation function that serves as a white reference for obtaining white reference data for correcting the reference level of the read data in the reading unit 132 and the distribution in the main scanning direction. The background rotators 140a and 140b have different diameters. The reason for using the background rotators 140a and 140b with different diameters is that the image forming apparatus 100 conveys sheets S of various thicknesses and has multiple backgrounds to ensure a stable reading focal length. Note that in this embodiment, two background rotators serving as white references are provided, but this is not limited thereto, and three or more background rotators may be provided.

[0029] Additionally, the background switching revolver 140 includes background rotors 140c and 140d that serve as non-white background portions to distinguish between the sheet S and the background when detecting a printed matter printed on a multicolored sheet S. The background rotors 140c and 140d have different diameter sizes. Note that, although the background rotors 140c and 140d are shown as black backgrounds in this embodiment, the present invention is not limited to this.

[0030] As described above, the background switching revolver 140 is equipped with four types of background rotating bodies. The background switching revolver 140 rotates according to the information (thickness, color) of the sheet S and the operation mode, and can be switched to any background rotating body.

[0031] In the first reading unit 130a, the background switching revolver 140 is disposed above the conveying path 122, and the irradiation unit 131 and the reading unit 132 are disposed below the conveying path 122.

[0032] Next, a description will be given of the hardware configuration of the image reading unit 130. Here, FIG.

[0033] As shown in FIG. 3, the first reading unit 130a and the second reading unit 130b of the image reading unit 130 include an image sensor 132a, lighting devices 131a and 131b, motors 141a to 141d that rotate and drive the background rotors 140a to 140d of the background switching revolver 140, an image processing unit 133, and a control unit 150.

[0034] The image processing unit 133 detects abnormalities (streaks, missing parts, stains), color changes, print position on the sheet S, etc. in the printed matter formed on the sheet S, and functions as a foreign matter detection unit that detects that an abnormal image has been printed by detecting a difference greater than a specified value by comparing the data with the original data. When the image processing unit 133 detects that an abnormal image has been printed, it instructs the control unit 150 to stop printing or display an alert.

[0035] The control unit 150 includes a CPU (Central Processing Unit) 151 that controls the operations of the image sensor 132a, the lighting devices 131a and 131b, and the motors 141a to 141d, a motor driving unit 152 that drives the motors 141a to 141d in response to instructions from the CPU 151, and a memory unit 153.

[0036] The motor driving unit 152 drives the motors 141a to 141d. When the motor driving unit 152 drives the motors 141a to 141d, the background switching revolver 140 operates.

[0037] The storage unit 153 stores a program that stores control timings of the image reading unit 130, such as image inspection timings, drive timings of the motors 141a to 141d, and the like.

[0038] When the image reading unit 130 functioning as an image inspection device is incorporated into the image forming apparatus 100, a control unit that triggers the execution of image inspection by communicating with the CPU 151 and a display unit that triggers the operation of the control unit are provided. When an abnormality is confirmed in the detection results by the image reading unit 130, the CPU 151 displays a status or gives maintenance instructions on the display unit via the control unit. The comparison / determination of the original data and the image reading results performed by the image processing unit 133 may be performed by the control unit that stores the original data.

[0039] Here, consider a case where foreign matter such as paper dust, dirt, toner, or ink adheres to part of the reading path of the image reading unit 130 of the image forming apparatus 100. Note that foreign matter comes in a variety of sizes, shapes, and colors.

[0040] First, we will explain what happens when a foreign object adheres to the background rotator 140a of the background switching revolver 140. If a foreign object adheres to the background rotator 140a of the background switching revolver 140, the foreign object will affect the original main scanning distribution shape when acquiring the reference white data, and therefore it is necessary to rotate the background rotator 140a to shift the reading position and acquire the desired data. However, when reading the image of the sheet S, the background of the background rotator 140a is hidden by the sheet S when reading the sheet S, and during image inspection, the rotation of the background rotator 140a allows reading to be performed at a shifted position (= a location without foreign objects), so removing the foreign object during maintenance is not necessarily required.

[0041] Furthermore, in the prior art (JP Patent Publication No. 2018-182529), the area from which the white reference data is acquired is limited to both ends of the main scanning direction, and the main scanning distribution is generated by estimation, which has the disadvantage of low accuracy, and the disadvantage of not being able to take care of cases where foreign matter adhesion occurs, as it is not limited to the area from which the white reference data is acquired.

[0042] Next, a case where a foreign substance adheres to the illumination devices 131a, 131b or the glass 131c of the illumination unit 131 will be described. If a foreign substance adheres to the illumination devices 131a, 131b or the glass 131c, it will appear in the read data because their positions are optically fixed. Therefore, any foreign substance adhered to the illumination devices 131a, 131b or the glass 131c requires removal by maintenance.

[0043] Therefore, in this embodiment, whether maintenance is necessary or not is determined depending on the location of the foreign matter inside the image reading unit 130, and if it is determined that maintenance is not necessary, the image inspection is continued. This point will be described in detail below.

[0044] 4-1 and 4-2 are diagrams illustrating exemplary read data related to the presence or absence of foreign matter on the background rotating body. As shown in FIGS. 4-1 and 4-2, the image reading unit 130 reads the background rotating body as white reference level data and main scanning distribution correction data. Note that the image reading unit 130 reads the background rotating body in advance before initial adjustment of the image forming apparatus 100 or before reading the sheet S.

[0045] Figure 4-1 shows an image of a foreign substance adhering to the reading line of the image reading unit 130 on the background rotating body 140a. When a reading line containing such a foreign substance is read, the reading level at the foreign substance location changes, as shown in the graph in Figure 4-1, and the data cannot be used as correction data for the main scanning distribution. However, by detecting a drop in the reading level, it is possible to determine that a foreign substance (or an optical abnormality) has adhered.

[0046] Therefore, to determine whether the problem is foreign matter or an optical anomaly, the background rotator 140a is rotated and the reading line position is changed, as shown in FIG. 4-2. By changing the reading line position, it is possible to obtain data without a decrease in the reading level, as shown in the graph in FIG. 4-2, and it is clear that the foreign matter was attached to the background rotator 140a. At this time, the image forming apparatus 100 can be stopped and maintenance can be started to remove the foreign matter, but since this does not cause any inconvenience when performing image inspection, it is acceptable to leave it as it is.

[0047] FIG. 5 is a diagram illustrating exemplary read data related to the presence or absence of foreign matter in illumination devices 131a and 131b. The example shown in FIG. 5 illustrates a state in which foreign matter has adhered to illumination devices 131a and 131b, which are configured with LED (Light Emitting Diode) arrays. As shown in FIG. 5, the foreign matter adhered to illumination devices 131a and 131b causes vignetting of the light emitted from illumination devices 131a and 131b, preventing sufficient light from reaching the illuminated target, resulting in a reduction in the level of some of the read data. Unlike a rotatable background rotating body, illumination devices 131a and 131b (or glass 131c) cannot move the position of foreign matter. Therefore, unless the foreign matter adhered to these devices is removed, the foreign matter will always affect the read image, preventing the image forming apparatus 100 from functioning properly.

[0048] Next, the read image and how the foreign matter appears will be described, with reference to Fig. 6, which is a diagram for explaining an example of the read image and how the foreign matter appears.

[0049] 6(a) shows a case where foreign matter is attached to the background rotating body 140a, and shows a read image (first read image) in a state where the sheet S is not passing through. In other words, when the background rotating body 140a with foreign matter attached is on the reading line, it looks like FIG. 6(a).

[0050] Fig. 6(b) shows a read image (first read image) read while rotating the background rotator 140a having the foreign matter attached thereto shown in Fig. 6(a). When acquiring white reference data, the background rotator 140a is rotated to acquire background data at a location free of foreign matter in order to prevent the foreign matter from interfering with the reading line.

[0051] 6(c) shows a case where foreign matter adheres to the irradiation unit 131 (or the glass 131c) and a read image (first read image) is obtained when the sheet S is not passing through. The foreign matter adhered to the irradiation unit 131 (or the glass 131c) blocks light, causing streaks in the sub-scanning direction as shown in FIG. 6(c).

[0052] Figure 6(d) shows a read image (second read image) that does not pose a problem in image inspection when image inspection is performed in the state shown in Figure 6(a) or Figure 6(b), because any foreign matter attached to the background rotating body 140a will be hidden by the sheet S being inspected.

[0053] Figure 6(e) shows a read image (second read image) in which false defects occur due to the image inspection, because the printed sheet S is read including light vignetting when performing image inspection in the state shown in Figure 6(c). Image inspection cannot be performed in this state.

[0054] Next, the process of detecting the location of foreign matter attachment will be described with reference to the flowchart of FIG.

[0055] 7, the image processing unit 133 turns on all of the lighting devices 131a and 131b of the irradiation unit 131 (step S1). When there are multiple irradiation units 131, the image processing unit 133 turns on all of them. When the irradiation unit 131 is a single light, the image processing unit 133 may turn on only a portion of them.

[0056] Next, the image processing unit 133 controls the image sensor 132a to read the background rotating bodies 140a to 140d (step S2).

[0057] Next, the image processing unit 133 checks whether or not there is a foreign substance (whether or not there is a drop in the main scanning distribution) from the data acquired from the image sensor 132a (step S3).

[0058] If the image processing unit 133 determines that no foreign matter is present (No in step S3), it ends foreign matter detection and can operate as an image inspection device.

[0059] When the image processing unit 133 determines that there is a drop in the main scanning distribution and that there is a foreign substance (Yes in step S3), it starts narrowing down the adhesion location.

[0060] First, the image processing unit 133 rotates the background rotators 140a to 140d (step S4) to move the foreign object away from the reading line.

[0061] Next, the image processing unit 133 controls the image sensor 132a to read the background rotating body (step S5).

[0062] Next, the image processing unit 133 checks whether or not there is a foreign substance (whether or not there is a drop in the main scanning distribution) from the data acquired from the image sensor 132a (step S6).

[0063] If the image processing unit 133 determines that there is no foreign matter (No in step S6), the foreign matter is attached to the background rotating bodies 140a to 140d, and there is no problem with operating the image inspection device by shifting its position in step S4, so the detection process is terminated.

[0064] If the image processing unit 133 determines that there is a drop in the main scanning distribution and that there is a foreign object (Yes in step S6), this means that the foreign object is attached to the optical system, such as the glass 131c, other than the background rotating bodies 140a to 140d, and so continues to narrow down the location to encourage user maintenance.

[0065] Next, the image processing unit 133 turns on only one of the illumination devices 131a and 131b of the illumination unit 131 (for example, illumination device 131b) of the illumination unit 131, which had been fully turned on up until now (step S7). Note that, in the case where the illumination unit 131 is only one illumination device in the system, the image processing unit 133 turns on only a narrowed illumination area.

[0066] Next, the image processing unit 133 controls the image sensor 132a to read the background rotating bodies 140a to 140d (step S8).

[0067] Next, the image processing unit 133 checks the presence or absence of foreign matter (whether there is a drop in the main scanning distribution) from the data acquired from the image sensor 132a (step S9). At this time, the overall reading level is lowered because the illumination of the illumination device of the irradiation unit 131 is reduced, but the presence or absence of an abnormality is determined from the distribution shape.

[0068] If the image processing unit 133 determines that there is no foreign matter (No in step S9), it assumes that the foreign matter is attached to the turned-off lighting device 131a of the irradiation unit 131, and issues an instruction to clean the lighting device 131a (step S10), and ends foreign matter detection.

[0069] If the image processing unit 133 determines that there is a drop in the main scanning distribution and that there is a foreign object (Yes in step S9), the foreign object is attached to the lit illumination device 131b of the irradiation unit 131 or another optical system such as the glass 131c, and the image processing unit 133 further narrows down the range.

[0070] Next, image processing unit 133 switches between turning on and off lighting device 131a and lighting device 131b of irradiation unit 131 (step S11). Note that, when irradiation unit 131 has only one lighting device in the system, image processing unit 133 lights up a narrowed portion of the lighting area.

[0071] Next, the image processing unit 133 controls the image sensor 132a to read the background rotating bodies 140a to 140d (step S12).

[0072] Next, the image processing unit 133 checks whether or not there is a foreign substance (whether or not there is a drop in the main scanning distribution) from the data acquired from the image sensor 132a (step S13).

[0073] If the image processing unit 133 determines that there is no foreign matter (No in step S13), it assumes that the foreign matter is attached to the turned-off lighting device 131b of the irradiation unit 131, and issues an instruction to clean the lighting device 131b (step S14), and ends foreign matter detection.

[0074] If the image processing unit 133 determines that there is a drop in the main scanning distribution and that there is foreign matter (Yes in step S13), it issues a cleaning instruction (step S15) assuming that the foreign matter is attached to the optical system such as the glass 131c other than the background rotating bodies 140a to 140d, and ends the detection process.

[0075] As described above, by detecting foreign matter and determining where it is attached, and if no maintenance (i.e. cleaning) is required, the device can continue to be used, but if maintenance is required, an alert will be displayed on the display, thereby avoiding unnecessary declines in productivity.

[0076] As described above, according to this embodiment, the image processing unit determines whether the abnormality (dust adhesion) appears in the scanned image or is hidden in the scanned image, thereby preventing the false detection of defects in a normal printed image due to foreign matter in the image inspection device itself. As a result, if it is determined that foreign matter adhesion is affecting the image inspection, the image inspection can be stopped or an alert can be issued to instruct maintenance to prevent false detection, thereby preventing unnecessary declines in productivity and loss of recording media. Furthermore, the location of the abnormality can be identified, leading to the issuance of maintenance instructions.

[0077] In this embodiment, the image reading unit 130 that reads the sheet S includes the reading unit 132, which is a reduction optical system. However, this is not limited to this, and a contact image sensor (CIS) may also be used. FIG. 8 is a diagram showing a modified configuration of the second reading unit 130b. As shown in FIG. 8, the second reading unit 130b includes a line image sensor 160 in which a plurality of image pickup elements that perform photoelectric conversion for each pixel are arranged one-dimensionally in the sheet width direction. The image pickup elements that make up the line image sensor 160 are optical sensors that perform an operation of reading the image on the sheet S at the reading position.

[0078] (Second embodiment) Next, a second embodiment will be described.

[0079] The second embodiment differs from the first embodiment in that the image processing unit excludes read streaks caused by foreign matter that coincide with the detected foreign matter in the main scanning direction from the foreign matter adhesion detection results. In the following explanation of the second embodiment, explanations of the same parts as in the first embodiment will be omitted, and only differences from the first embodiment will be explained.

[0080] FIG. 9 is a diagram showing an example of foreign substance inspection during shading according to the second embodiment. The image reading unit 130 is provided with a reference member, which is a reference white board used to correct various distortions in the reading optical system, etc. The image reading unit 130 performs shading correction during image reading based on the reading results of the reference member. As shown in FIG. 9, if an abnormality occurs in a pixel value due to the adhesion of a foreign substance, the read data value of the background rotating bodies 140a to 140d at the pixel position corresponding to the location where the abnormality occurs will be smaller than that of the surrounding pixels (shown by a solid line in FIG. 9).

[0081] The read data of the reference member shown in Fig. 9 (reference member data: second read image) varies gradually in the main scanning direction due to uneven illumination of the irradiation unit 131 or uneven sensitivity of the imaging element of the image sensor 132a. Therefore, the image processing unit 133 shifts the reference position of the reference member data in the main scanning direction (shown by the large dashed line in Fig. 9). Furthermore, the read data of the background rotating bodies 140a to 140d shown in Fig. 9 (background board data: first read image) will have the same main scanning distribution as the reference member data (shown by the small dashed line in Fig. 9).

[0082] As shown in Figure 9, when comparing the reference member data with the background board data after changing the reference position, differences in components that change gradually in the main scanning direction even when there is no abnormality appear, as well as differences in components that change suddenly when there is an abnormality. The latter sudden change component due to an abnormality appears in two places, shifted in the main scanning direction by the amount the reference position was shifted.

[0083] The image processing unit 133 detects abnormal pixels from the data obtained by the comparison. The data after this comparison needs to be data equivalent to the data after shading correction. This is because abnormal pixels are determined using an appropriate threshold value based on the degree of influence in the data after shading correction. Therefore, this comparison is realized by calculating the ratio of two pieces of data, similar to the calculation performed in shading correction. By performing this calculation to calculate the ratio, components of pixel values ​​that change gradually in the main scanning direction are roughly uniform, thereby minimizing pixel value fluctuations in the main scanning direction and preventing erroneous detection when detecting abnormal pixels. On the other hand, components that change sharply due to abnormalities such as the adhesion of foreign matter are not uniform even when compared, so they can be detected as abnormal.

[0084] These functions enable the image reading unit 130 of this embodiment to perform highly accurate anomaly detection. The image processing unit 133 detects anomalies using a threshold that takes into account the degree of influence of the data after shading correction, thereby improving the accuracy of anomaly detection.

[0085] Fig. 10 shows an example of the image reading result when a foreign substance is present. As shown in Fig. 10, reading line 1 is the read image when a foreign substance adheres to the glass 131c after shading. Reading line 2 is the read image when a foreign substance is present during shading.

[0086] 9, foreign matter inspection during shading can be performed, but if foreign matter on the background rotating bodies 140a to 140d or the glass 131c cannot be cleaned, the foreign matter will appear as reading streaks on the read image. Images with reading streaks like this will be notified as abnormal images.

[0087] Therefore, by comparing the read streaks during shading with those during image inspection, abnormalities at the same main scanning position are excluded from the abnormal image. This makes it possible to reduce the number of unnecessary abnormal images detected due to foreign matter.

[0088] Furthermore, if a foreign object adheres to the glass 131c after shading, it cannot be detected as a reading streak even when compared with the time of shading.In this way, foreign objects that adhere during the process can be determined to be foreign objects by using the margin area, which is an area outside the paper.Furthermore, reading streaks caused by foreign objects continue to be detected in the sub-scanning direction and are also detected in the margin area, which is an area outside the paper, so that areas where reading streaks occur in the margin area at the leading and trailing edges of the image can be determined to be foreign objects.

[0089] In addition, because shading is performed while the paper is passing, foreign matter that adheres to the glass 131c or background rotating bodies 140a to 140d while the paper is passing can be detected later with high accuracy, as explained in Figure 9. Note that by comparing this with the main scanning position detected as an abnormality before shading, it is also possible to determine whether or not there is a read streak. If the main scanning positions match, the display unit will notify the user that there is a possibility of a read streak for the detected abnormality, eliminating the need to check a large number of abnormal image detection results.

[0090] According to this embodiment, if a foreign object is found, comparing the read data (reference object data) of the reference object whose reference position has been changed with the read data (background object data) of the background rotating bodies 140a-140d reveals the difference in the sharply changing components, making it possible to detect the foreign object. By excluding main-scanning position abnormalities where foreign objects are detected in the foreign object inspection results during shading from the abnormal image, it is possible to reduce the detection of unnecessary abnormal images caused by foreign objects. Furthermore, by comparing the information determined to be an abnormal image with foreign object detection during printing, it is possible to retroactively eliminate the influence of foreign objects.

[0091] The program executed by the image reading unit 130 of this embodiment is provided as a file in an installable or executable format recorded on a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disc).

[0092] The program executed by the image reading unit 130 of this embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. The program executed by the image reading unit 130 of this embodiment may be provided or distributed via a network such as the Internet.

[0093] Furthermore, the program executed by the image reading unit 130 of this embodiment may be provided by being pre-installed in a ROM or the like.

[0094] In the above embodiment, the reading device and image forming device of the present invention are described as being applied to a multifunction device having at least two of the functions of a copy function, a printer function, a scanner function, and a facsimile function, but the present invention can be applied to any reading device or image forming device such as a copier, printer, scanner device, or facsimile device.

[0095] Furthermore, the image reading unit 130 of this embodiment is not limited to having the first reading unit 130a that reads the first side of the sheet S and the second reading unit 130b that reads the second side of the sheet S. For example, the reading unit 130b may be disposed between the fixing roller 123 and the conveying path switching unit 124. In this case, the sheet S read by the reading unit 130b is turned over, an image is formed on the sheet S by the image forming unit 110, and then the sheet S is read again by the reading unit 130b. [Explanation of symbols]

[0096] 100 Reading device, image forming device 110 Image forming unit 130 Image reading unit 131a,131b Lighting equipment 133 Foreign object detection unit 140a~140d Background part S Recording Media [Prior art documents] [Patent documents]

[0097] [Patent Document 1] Japanese Patent Application Publication No. 2018-182529

Claims

1. an image reading unit that reads an image on a conveyed recording medium; a background portion that serves as a background for image reading by the image reading unit; a foreign matter detection unit that compares a first read image obtained by reading the background portion with the image reading unit and a second read image obtained by reading the background portion and the recording medium with the image reading unit to detect adhesion of foreign matter to a part of the reading path of the image reading unit and the location of the adhesion of the foreign matter; Equipped with When the foreign matter detection unit determines that the location of the foreign matter is a location that will be hidden by the recording medium when the image reading unit reads the recording medium, it is determined that there is no need to remove the foreign matter. A reading device characterized by:

2. the background portion is rotatable by a motor, the first read image is an image read by the image reading unit while rotating the background portion in a state where the recording medium is not overlapped with the background portion; 2. The reading device according to claim 1, wherein:

3. the image reading unit includes a plurality of illumination devices, and performs image reading by switching on and turning on the illumination devices of the image reading unit; 2. The reading device according to claim 1, wherein:

4. the image reading unit includes a first lighting device and a second lighting device, and switches between turning on and off the first lighting device and the second lighting device; 4. The reading device according to claim 3, wherein:

5. the foreign matter detection unit excludes a read streak caused by a foreign matter that coincides with the detected foreign matter in the main scanning direction from the detection result of foreign matter adhesion; 5. The reading device according to claim 1, wherein the reading device is a reading device for reading a document.

6. the foreign matter detection unit detects adhesion of foreign matter after image formation on the recording medium.

6. The reading device according to claim 5, wherein:

7. the foreign matter detection unit notifies the detection result when the main scanning position of the detected foreign matter coincides with that of a previously detected foreign matter; 7. The reading device according to claim 5 or 6.

8. the foreign matter detection unit determines whether a foreign matter exists based on a read streak outside the area of ​​the recording medium.

8. The reading device according to claim 5, wherein the reading device is a reading device for reading a document.

9. A reading device according to any one of claims 1 to 8; an image forming unit; An image forming apparatus comprising:

Images